1. Field of the Invention
The present invention relates to a display device, and more particularly to a technique which is effectively applicable to a liquid crystal display device.
2. Description of Related Art
Conventionally, as a liquid crystal display device, there has been known an active-matrix type liquid crystal display device which uses TFT elements as switching elements. The active-matrix type liquid crystal display device is, for example, configured such that, on one substrate out of a pair of substrates which constitutes a liquid crystal display panel, a plurality of scanning signal lines, a plurality of video signal lines which stereoscopically intersects the plurality of scanning signal lines by way of an insulation layer, TFT elements and pixel electrodes which are arranged in pixel regions each of which is surrounded by two neighboring scanning signal lines and two neighboring video signal lines are arranged. Here, the TFT element which is arranged in each pixel region has a gate electrode thereof connected to the scanning signal line, a drain electrode thereof connected to the video signal line and a source electrode thereof connected to a pixel electrode. Hereinafter, the active-matrix type liquid crystal display device is simply referred to as a liquid crystal display device.
In the liquid crystal display device, when a malfunction occurs in the TFT element, it becomes impossible to apply a gray scale voltage (video signal) to the pixel electrode which is connected to the source electrode of the TFT element and hence, a point defect which is referred to as a dot omission phenomenon occurs. Accordingly, in a recent liquid crystal display device, there may be a case that a spare TFT element (also referred to as a floating TFT) is arranged in each pixel region (for example, see patent document 1).
With the provision of the spare TFT element in the pixel region, when the malfunction occurs in the TFT element which is used in an initial state, for example, by cutting away the drain electrode of the TFT element in which the malfunction occurs from the video signal line, by connecting the drain electrode of the spare TFT element to the video signal line, and by connecting the source electrode of the spare TFT element to the pixel electrode, it is possible to avoid the occurrence of the point defect.    Patent document 1: JP-A-7-104311